Shaky Ground

On one hand, it's been decades since a widespread disease outbreak crippled the U.S. cattle economy and filled pits with euthanized carcasses. In fact, in today's highly mobile world of global trade, it's almost miraculous that the U.S. has kept foot-and-mouth disease (FMD) at bay since 1929. After all, the disease existed in Mexico until 1953, when the border was even more porous than today. On the

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On one hand, it's been decades since a widespread disease outbreak crippled the U.S. cattle economy and filled pits with euthanized carcasses.

In fact, in today's highly mobile world of global trade, it's almost miraculous that the U.S. has kept foot-and-mouth disease (FMD) at bay since 1929. After all, the disease existed in Mexico until 1953, when the border was even more porous than today.

On the other hand, the tick that harbors Heartwater — a disease some veterinarians view as more catastrophic than FMD — has made its way from Africa to Puerto Rico.

Moreover, Mel Pence, points out, “When you look at reproductive efficiency in the industry, when you look at disease in the nation's feedlots and the horrendous amount of money we pay for it, certainly diseases are severely impacting economic returns to the beef industry.” Pence is a veterinary field investigator and University of Georgia associate professor of large animal medicine who spent more than two decades in a private cow-calf practice in Iowa.

Global threats remain

From the standpoint of foreign animal disease (FAD), Pence explains, “FMD is the one we worry about the most. It's a devastating economic disease we can't afford to get.”

FMD is tough to detect at its early stages in sheep and goats because it doesn't affect them as severely as cattle, Pence says. As illustrated by the United Kingdom's outbreak in 2001, that means the disease can get a foothold across expansive geographic regions before folks even realize it's a problem.

Keep in mind that while morbidity runs high with this virulently contagious disease, FMD's mortality rate is actually quite low. It's the need to euthanize exposed animals for containment that's so catastrophic.

“The way FMD will be controlled is early detection,” Pence says. “I feel we've developed a solid infrastructure in this nation to handle it if, heaven-forbid, it ever turns up here again.” In other words, while devastating, FMD can be eradicated.

Unfortunately, that's not necessarily the case with Heartwater, which Pence believes also poses high FAD risk to U.S. producers. The morbidity and mortality rates of the most common acute form of this disease are staggering.

Since the disease organism is borne by tick, eradicating the disease would be next to impossible. That's because rather than eradicating exposed animals as with FMD, you'd have to eradicate all of the ticks.

If there's a silver lining, Pence notes, it's that these two diseases aren't zoonotic. In other words, unlike fears about a link between BSE in cattle and variant Creutzfeldt-Jakob Disease (vCJD) in humans, FMD and Heartwater pose negligible health risk to humans.

There are a host of other spooky FADs that impact cattle around the world, such as Rinderpest, Lumpy Skin Disease, Rift Valley Fever and Contagious Bovine Pleuropneumonia. And, there are FADs affecting other livestock species that have indirectly impacted U.S. cattle markets the past few years. Exotic Newcastle's Disease and avian influenza in the poultry industry come to mind.

But, Pence explains other than following regulations, awareness and observation, there's not much producers can do to prevent the diseases.

“It's pretty much out of a producer's control whether or not an FAD comes to the U.S.,” Pence explains. “It's controlled by regulations on importing cattle and cattle by-products.”

Domestic diseases of concern

Just the opposite is true of diseases the World Health Organization (WHO) traditionally classified as List A and List B diseases (Table 1, page 12). While eradication may not be possible, management and control rests in the hands of producers.

List A diseases are those WHO designates as having the potential for rapid spread, regardless of national borders, transmissible diseases that pose serious socio-economic or public health consequences, and are of major importance in the international trade of animals and animal by-products.

The List B designation is similar but denotes diseases posing significant socio-economic or public health consequences within a country, while also being of significant importance in the international trade arena.

You may be surprised to find some common cattle ailments on the list, such as leptospirosis, bovine fenital campylobacteriosis (vibriosis) and infectious bovine rhinotrachetis (IBR/red nose), which many U.S. producers manage for every day.

“Politico-economic considerations have something to do with the disease listing,” says John Maas. He explains some diseases endemic to the U.S. are ones other WHO members want to keep out of their countries. Maas is a Cooperative Extension veterinarian with the University of California-Davis.

Of course, you may also be amazed at some of the common diseases not on the list, such as persistently infected bovine viral diarrhea (BVD-PI), which U.S. producers are working harder to control.

Categorize and conquer

While it's impossible to make blanket recommendations for any disease, there are common approaches to assessing risk and management protocols that producers can use in disease management.

For instance, Pence suggests first deciding whether biosecurity or biocontainment is the goal. Biosecurity is either eliminating an existing disease in the herd or preventing the introduction of one. Brucellosis and tuberculosis (TB) are examples, while others might include BVD-PI and Johne's disease.

If it's impossible or impractical to remove something from the environment or herd, biocontainment aims at management that allows living with the disease economically.

Leptospirosis and IBR would be examples.

Whatever the disease challenge, Pence explains it will likely come under one of three categories: neonatal enteric disease, reproductive or respiratory.

Likewise, Maas points out disease transmission will either be classified as viral, rickettsial (borne by ticks, lice and mites), animal-to-animal or feed borne.

Once you know which category the disease fits and its mode of transmission, you're well on the road to understanding risk factors associated with the disease and ways to mitigate them.

As an example, with viral disease the mode of transmission means you have to be concerned about the pathogen's physical introduction, be it on vehicles, visitors' clothes and boots, etc., Maas explains. With FMD, it could even be a visitor from an FMD country who harbors the organism in their respiratory tract, spreading the organism simply by coughing or sneezing.

Conversely, in diseases requiring animal-to-animal contact like BVD and IBR, this means figuring out how to keep cattle isolated and ensuring new additions don't bring it with them.

Disease organisms harbored by the environment (like anthrax), or borne by insect (like anaplasmosis) and wildlife (like rabies) vectors, are a tougher nut to crack.

As complicated as this sounds, Maas says most producers practice biosecurity and biocontainment daily, though they may not think of it in those terms. For instance, when you buy a bull, chances are you make sure he's TB- and brucellosis-free and tested for trichomonosis. That's biosecurity.

“Some producers know intuitively about biosecurity. They only buy cattle from certain herds and only run specific types of cattle in certain parts of the country,” Maas says.

Carrying the bull example a step further, Pence applies the four basics of biosecurity — isolate, test, vaccinate and possibly medicate. Say you've decided to buy Old Grumpy 319, a known son of Grouchy's Lament. You'll make sure he's received basic vaccinations including lepto and IBR, and he's been tested for TB, brucellosis and trichomonosis. If your herd's BVD-PI free, you'll test for that, too. Once he's home, you'll isolate him for 30-60 days.

2003 U.S. cattle health status reported to World Health Organization (formerly classified as List A and List B diseases)

Disease (class)

Outbreaks

Cases

Deaths

Destroyed

Slaughtered

Control measures

Anaplasmosis*** (B)

Vaccination where practical

Anthrax** (B)

Vaccination where practical

Bluetongue* (A****)

Border precautions/monitoring

Bovine babesiosis** (tick fever) (B****)

Modified eradication, notification required Control of anthropods, border precautions, zoning Endemic in Puerto Rico and U.S. Virgin Islands — last reported case on mainland in 1943.

If he has an infectious disease, he'll get over it in time, develop immunity and won't be shedding the pathogen, Pence says. Plus, since you'll probably want to vaccinate him for the same diseases you guard your cow herd against, the isolation time gives the bull a chance to build immunity.

“There are areas of the U.S. where the bull may be exposed to lepto hardjobovis, so you may want to treat with tetracycline to reduce the potential of introducing a carrier for that disease into the herd. That treatment is also effective for anaplasmosis,” he says.

In every case, Pence explains, “The people who know best what to vaccinate for in your area are you and your veterinarian. The local practitioner should be able to help you build a biosecurity plan.”

Basic disease prevention

Of course, all this management is wasted without the essential foundation of a health program.

“Nutrition plays a major role,” Pence says. “The macronutrient needs of energy and protein must be met, but we also know micronutrients like copper and selenium impact an animal's ability to develop immunity. And, we know some areas of the country are deficient in these minerals.”

As far as Pence is concerned, control of internal parasites is part of nutrition since worm burdens suppress appetite and create nutritional deficits.

Next comes the basic vaccination protocol, relative to a producer's goals and the disease challenges in the area and on the farm. For most producers, Pence says that means calves should be vaccinated with Black Leg and a four-way viral (IBR, BVD, BRSV, PI3) by the time they're 4-6 months old.

Similarly, when it comes to cows and reproductive failure, Pence explains the most likely candidates are always IBR, BVD, lepto and vibriosis.

Pence says he's seeing more and more producers in Georgia isolate and test specifically for BVD-PI. “The technology and knowledge associated with this disease have expanded so rapidly in the past 10 years that we're at a point where we really can eradicate it from the farm,” he says.

Maas is seeing the same thing in California for both BVD-PI and Johne's disease. He equates increased testing to the early-innovator phase of new technology adoption. “We're seeing 5-10% of our producers now doing some kind of testing,” he says.

Hand in hand with this is the opportunity producers have to maintain and add value by documenting health management. At the very least, Pence suggests producers keep health records “to validate you're doing everything possible to reduce the spread of disease.”

Likewise, Maas says, “Producers should probably be keeping a record of health management that shows they're at least performing at the industry standard, particularly in the case of diseases like Johne's where negligence could be involved.”